1. Field of the Invention
The present invention relates to a technique of carrying and locating a sheet frame, which is employed for transferring a lead frame having a resin-molded semiconductor device from a step to another step in steps of fabricating a semiconductor device, for example.
2. Description of the Background Art
&lt;Structure of the Prior Art&gt;
Steps of fabricating a semiconductor device include a step of molding a semiconductor chip which is mounted on a lead frame with resin and a step of molding a subsequent lead frame. Between these two steps, it is necessary to carry the preceding lead frame from the former step to the latter step while locating the same at a prescribed position. FIGS. 13 and 14 are a plan view and a front elevational view showing a sheet frame employed for such a purpose.
Referring to these figures, a lead frame 1 having a prescribed width and a prescribed length is mounted on a lower rail 21 which is provided on a sheet frame carrying-and-locating apparatus 2. A completely resin-molded semiconductor device 1a is integrated in the lead frame 1. Guide bars 21a are fixedly mounted on the lower rail 21, while a pair of upper rails 22a and 22b are slidably supported by the guide bars 21a to be movable along a horizontal shorter-side direction X of the lead frame 1. A pair of fixed upper rails 23a and 23b are provided on the lower rail 21 adjacently to the upper rails 22a and 22b. Guide spaces 24, which are clearances for guiding the lead frame 1, are defined between the pair of upper rails 22a and 22b, being most approached to each other in closed states, and the lower rail 21. Similar guide spaces 24 are also defined between the pair of fixed upper rails 23a and 23b and the lower rail 21.
The apparatus 2 is provided with a pair of drive units 25, which are adapted to drive the pair of upper rails 22a and 22b in the shorter-side direction X respectively to bring the same into separated (open) states or closed states at need. The apparatus 2 further comprises a carrier 26 for carrying the lead frame 1, whose end portions are stored in the guide spaces 24, in a horizontal carriage direction Y, shown by arrow in FIG. 13, longitudinally along the lead frame 1 with a prescribed distance, a drive unit 27 for driving the carrier device 26, a stopper 28 for stopping the as-carried lead frame 1 at a prescribed position, and a drive unit 29 for upwardly and downwardly driving the stopper 28.
&lt;Operation of the Prior Art&gt;
The conventional apparatus 2 operates as follows: First, the drive units 25 so operate that the pair of upper rails 22a and 22b are guided by the guide bars 21a to slide in directions to be separated from each other (open directions), to enter open states. Then, the lead frame 1 is placed on the lower rail 21 by action of a supplier (not shown) from above the lower rail 21. Thereafter the upper rails 22a and 22b slide toward each other along the shorter-side direction X, to enter closed states. At this time, the upper rails 22a and 22b define the guide spaces 24 with the lower rail 21, to hold cross-directional end portions of the lead frame 1 therein.
Then, the lead frame 1 is carried by the carrier 26, which is driven by the drive unit 27, along the carriage direction Y with a prescribed distance. The lead frame 1 is stopped at a prescribed position by the stopper 28 which is located on an upper direction. At this time, cross-directional end portions of the lead frame 1 are held in the other guide spaces 24 defined by the fixed upper rails 23a and 23b and the lower rail 21 so that the position of the lead frame 1 is settled in the shorter-side direction X, while the same is stopped by the stopper 28 so that its position is settled in the longitudinal direction. The lead frame 1 thus located in a prescribed position is then held by a transfer device (not shown) and the stopper 28 is downwardly driven by the drive unit 29, to release the lead frame 1 from the stopped state. After the lead frame 1 is transferred to a next fabrication step by the aforementioned transfer device, the stopper 28 is upwardly moved to the original upper direction, while the carrier 26 also returns to its original position. The aforementioned steps are so repeated as to carry and locate a plurality of lead frames.
&lt;Problems of the Prior Art&gt;
In the conventional apparatus 2, the lower rail 21 is fixed at a constant position, and the stopper 28 is moved along the carriage direction Y by a constant distance. In order to carry and locate lead frames 1 of various dimensions, therefore, it is necessary to prepare such apparatuses in response to the dimensions. In other words, the conventional apparatus 2 is inferior in workability and economy for carriage and location of a plurality of types of lead frames 1. This problem is particularly serious in the field of the so-called multi-item small-quantity production for a number of types of lead frames 1 with small quantities.
In the aforementioned apparatus 2, further, the upper rails 22a and 22b slide along the shorter-side direction X. If the lead frame 1 is so deformed that the end portions along the shorter-side direction X cannot be stored in the guide spaces 24, therefore, the upper rails 22a and 22b interfere with the deformed portion upon sliding toward the closed states, to damage the lead frame 1.